Interfaces in Photovoltaic Materials

Silicon surface passivation

Silicon solar cells capture solar energy when light is absorbed near the cell’s surface. Efficiency in the most advanced silicon solar cells is limited by recombination of photo-excited electron-hole pairs at surfaces and interfaces. The surface of the cell represents a major material defect where loss of charge carriers may occur. Future generations of industrial high efficiency solar cells will require cost effective techniques for producing semiconductor/dielectric interfaces with very low rates of recombination. The process of creating these low recombination interfaces is known as surface passivation and its development is critical to the next generation solar cells. Existing work in the lab has produced record breaking surface passivation using charge extrinsically added to dielectric coatings. The problem, however, is that the passivation produced is not stable over a period of years as required for solar cells in the field. This area aims to explore a new generation of cost effective dielectric coatings that provide optimal passivation using the technologies proposed and patented by the group, as well as improving the optical qualities over current industrial films. This involves deposition of dielectrics using semiconductor facilities and characterisation of their properties using electronic techniques. These films will then be extrinsically treated to exploit their passivation characteristics.

Seminal work:

Passivating and selective contacts

While conventional silicon solar cells are a strong technology, an overwhelming drawback is the use of very high doping in contacts and carrier separation layers. This prevents further increases in their power conversion efficiencies. Passivating carrier-selective contacts have been recently demonstrated using metal oxide thin films. These materials can allow cell architectures that overcome the drawbacks of current technologies. In the lab we aim to study and develop passivating selective contacts based thin interfacial films, including device design and processing that enables their adoption and deployment in cell manufacture.

Seminal work:

Field-induced Optoelectronic Devices

Field-effect doped p-n junctions have long been proposed yet substantial advances were only recently achieved with a ~18% solar cell, and a field-effect photodiode. These, however, used intrinsically charged dielectrics limited to charge densities of ~1012 e/cm2. By tackling charge control we aim to take these devices to the next level using dielectrics with charge densities exceeding 1013 e/cm2. We intend to extend the application of ion-charged dielectrics to the formation of both n- and p-type field-effect doping. Both n- and p-type layers can be combined to form the new optoelectronic devices architerctures, most notable solar cell devices.

Seminal work: